This invention is concerned with compositions, and relates in particular to powder compositions and spray compositions that can be employed to reduce or even remove objectionable smells.
Undesirable odours are a nuisance in many situations; unpleasant smells may at best put people off their work, while at worst they may actually make them feelxe2x80x94and perhaps bexe2x80x94physically sick. Because the human nose can detect smells at active-ingredient levels as low as one part per billion (1 ppb), far below what most analysing equipment can detect, it is difficult to document such reductions by instrumental methods, and there is a serious problem in reducing or removing smells so as to improve the environment.
The molecules of substances that cause smells can range widely in both size and chemical nature. Some are large, and possibly filterable; others are not only too small to be removed that way, they are so small that they can stay suspended in the air for long periods. Some are hydrophobic (and so usually water-insoluble), such as the paraffins/hydrocarbons/mineral oils like diesel and gasoline and many fat soluble esters used as flavour ingredients, while others are hydrophilic (and so usually water-soluble), such as organic acids like butyric acid, (the xe2x80x9crancid butterxe2x80x9d smell) and many inorganic compounds like ammonia and hydrogen sulphide. The hydrophilic smell-forming materials can also be subdivided into those that are alkaline, such as ammonia and amines (which often smell fishy), those that are neutral, such as the alcohols (some of the C3-6 alcohols smell quite disgusting) and mercaptans giving odours typically related to decay of vegetables like cabbage, and those that are acidic, such as the butyric acid found in sour milk and butter products and the hydrogen sulphide found in rotten organic matter (the smell of a bad egg is mostly due to hydrogen sulphide).
In the past many attempts have been made to produce an all-purpose deodorizer, using many combinations of odour-combatting and masking chemicals. Some have been more successful than others, but none has proved truly victorious in the fight against smells. The present invention suggests a novel way of utilising some of the known chemicals, and even a novel combination of some of those chemicals, that seems to be significantly and perhaps surprisingly more effective than those presently available in the marketplace. This novel utilisation is based upon the use of amphoteric material, in particular sodium bicarbonate, in the form of an aqueous spray.
Amphoteric material has both acidic and basic properties, and so can form salts or adducts with both bases and acids. A well-known amphoteric compound is sodium bicarbonatexe2x80x94NaHCO3xe2x80x94also known as baking powder.
For many years it has been known that baking powder can be used to remove certain smells from refrigerators or on a surface by spreading it over that surface, leaving it to absorb the smell (no doubt at least partially by reacting chemically with the smell), and then wiping it up. However its acceptance has largely been limited to odour neutralisation in smaller household applications. This is probably due to its rather slow activity in odour removal because it has very limited capacity for most sulphides and mercaptans. It is also very sensitive to moisture; a 5% moisture content can often reduce the neutralisation capacity in respect of some odour molecules by more than 50%. A higher moisture content results in lumps forming which will reduce dramatically the active surface area and thus the neutralising capability. Furthermore, the consistency of baking powder is often such that it will create a very objectionable dust (irritating to breathe in and to have in skin contact). When such dust settles, it clings strongly to most surfaces and is even very difficult to remove by vacuum cleaning. These functional limitations may be the main reasons for its rather limited application and acceptance in the market over the years even though sodium bicarbonate has often been used as a relatively minor ingredient or filler substance in more complex deodorizing compositions.
U.S. Pat. No. 5,303,676 and U.S. Pat. No. 5,421,291 disclose an animal litter composition in which sodium bicarbonate or potassium bicarbonate is a minor ingredient. The composition comprises 1) a particulate, water-absorbent, clayey component, e.g., sodium bentonite, containing at least one water-swellable clay mineral, e.g., montmorillonite; and 2) a solid particulate deodorizing additive component comprising sodium bicarbonate or potassium bicarbonate, the particles of which are substantially coated with a mineral oil, mixed with a powdered siliceous material, e.g., expanded perlite, having a bulk density significantly lower than the density of sodium bicarbonate or potassium bicarbonate, the coated particles of sodium bicarbonate or potassium bicarbonate being stably adhered to and agglomerated with the particles of the. siliceous material. The animal litter composition contains about 80-98 weight %, preferably about 90-95 weight %, of clayey component provided by the sodium bentonite and about 2-20 weight %, preferably about 5-10 weight %, of deodorising additive component, provided largely by the bicarbonate. The composition may also optionally contain about 0.1 to 1 weight % of zinc oxide to exert a bactericidal action on the waste products in the litter.
GB-A-1356343 discloses a toilet-bowl-sanitising, foam-forming composition which may contain odour-improving additives or deodourising additives. In a particular example, three spray preparations are described. The preparations comprise 17; 23.40 or 22.20 parts of surface active agent(s), 0.1; 0.1 or 0.6 parts of disinfectant or germicide and 1 part alcohol, mixed with an aqueous solution comprising 80.35; 73.95 or 75.15 parts of water, and 1.5 parts of perfume. In a further example, a powder or granulate preparation is described comprising either 40 parts sodium carbonate and 40 parts citric acid, or 30 parts sodium carbonate and 50 parts sodium bisulphate, together with, in each case, 20 parts sodium lauryl sulphate and 0.3 parts fatty alcohol.
WO-A-98/27261 describes an animal care system desirably including animal litter with reduced malodour impression comprising solid moisture-absorbing material and effective amounts of both odour-absorbing material, preferably cyclodextrin or derivative thereof, and material for reducing the formation of malodour, e.g., antibacterial and/or urease inhibitor, preferably water-soluble metallic salt such as zinc salt. Behaviour control products are also provided including animal repellent and attractant products, preferably in spray containers, and freshening and cleaning products, also especially in spray containers, and, preferably, in association with instructions for using the products to carry out a method of animal control in which the animal litter is refreshed as needed, and areas are treated with repellent and attractant products to influence the animals to avoid certain areas and frequent other areas, and products for cleaning areas where accidents occur and discouraging the animal from returning to those areas.
According to one aspect of the present invention, there is provided a stock formulation useful in the preparation of a spray composition, the formulation comprising, as a major ingredient, amphoteric material and being dispersible in liquid to produce a spray composition containing by weight a relatively small proportion of the formulation in-a relatively large proportion of liquid.
The amphoteric material is preferably inorganic material since, as compared with organic materials, inorganic materials are less susceptible to degradation, especially microbiological degradation over time, i.e. inorganic materials tend to be more stable. The inorganic material may be a salt, particularly sodium bicarbonate or potassium bicarbonate. Another advantage is that such salts are often more readily dissolved in water to create a spray liquid than are many organic substances.
Most advantageously, the formulation is in the form of a powder.
By xe2x80x9cmajorxe2x80x9d herein is meant, on the basis of a percentage by weight of the entire formulation, occurring in at least twice the percentage of any other individual ingredient of the formulation or in about 50% or more.
Very preferably, the amphoteric material is uncoated. By xe2x80x9cuncoatedxe2x80x9d herein is meant not coated with any substance which significantly reduces that active surface area of the particles of amphoteric material available for reaction with gaseous odours. In particular, the formulation and the spray composition should be substantially free of oily matter.
We have found that if sodium bicarbonatexe2x80x94or, indeed, certain other amphoteric compoundsxe2x80x94is used not as a minor ingredient of a make-up formulation (from which there is made the desired xe2x80x9cusexe2x80x9d composition) but as a major one, and, optionally, when the formulation is a powder, is combined with a significant proportion of drying agent, then this provides a stock formulation from which an extremely efficient deodorising aqueous spray composition, particularly an aerosol spray composition, can be made.
This spray composition can be used within an area or on a surface where there is a smell (if on a surface it can be allowed to stand for a time to absorb or neutralise that smell). This astonishing effect of an amphoteric compound dissolved in water and applied/distributed in an aerosol spray is indeed surprising. Sodium bicarbonate applied as a dry powder for odour absorption is extremely moisture sensitive. Only some 5% increase in moisture content will often reduce the capacity for neutralisation of some odour molecules by more than 50%. Further exposure to moisture can cause lump formation, with rather drastic capacity reduction as a consequence. It is, however, known that sodium bicarbonate dissolved in water can have some odour neutralising effect, for example it can be used as a mouthwash or for soaking dirty diapers. This effect is most likely attributable to acid/base reaction and neutralisation processes but possibly also to weak adsorption effects of remaining active material when the washing process is completed. Only very small amounts of active material can be distributed in an aerosol spray. This makes it less obvious to use sodium bicarbonate in a spray composition for effective odour neutralisation. This is probably the reason why no-one has previously thought of applying an amphoteric compound, e.g. sodium bicarbonate, as the main active ingredient in an aqueous spray for in-air odour neutralisation.
The invention also provides a spray composition made by dispersing, preferably dissolving, the relatively small proportion of the stock formulation in the relatively large amount of liquid.
The stock formulations of the invention are to be used in the preparation of spray deodorizing compositions. This preparation involves dispersing the formulation, and preferably actually dissolving it, in water so that there is produced a suitable spray composition. More is said about this hereinafter.
Advantageously, the stock formulations are alkaline, i.e. have a pH higher than 7 when dissolved in water. A major advantage is that very many decomposition products of organic matter resulting in odour are acidic and therefore tend to be neutralised by an alkaline composition applied to them. Moreover, a majority of the malodours that people most object to in their daily environment, such as in their homes, are acidic.
The stock formulations comprise as a major ingredient amphoteric material (in the form of one or more amphoteric compounds), and, optionally as a significant other ingredient, a drying agent. The percentage of amphoteric material is very preferably at least 55%. One particularly-preferred formulation contains 60% amphoteric material. By xe2x80x9ca significant otherxe2x80x9d is meant that the amount of the drying agent is not small but equally is not so large that it could be thought of as the major ingredient. On the same percentage basis, there is desirably about 5% or more, sometimes at least 15%, and in some cases at least 25%, of the drying agent. Two formulations contain about 30% drying agent. A suitable drying agent is sodium sulphate, possibly with magnesium sulphate; another possible material for this purpose is potassium sulphate.
The invention""s stock formulations comprise amphoteric material as one major ingredient. The amphoteric compound of choice is sodium bicarbonate, but another possible such compound is potassium bicarbonate.
The invention""s spray composition can also include a preservant (otherwise known as a xe2x80x9cpreservativexe2x80x9d) to prevent microbiological growth. Such preservant, which is not necessary in the dry stock formulation (though it can be included therein), is preferably used in an amount of from about 7 ppm (0.0007%) to about 1 wt. % of the spray composition. Typical preservants are water water-soluble parabens usable in a total amount of about 0.5 wt. %, or sodium salts thereof. In other cases, an isothiazolinone material, for example xe2x80x9cKathon CGxe2x80x9d, (Trade Mark) can be used, in an amount of from about 7 ppm to about 20 ppm by weight to achieve compatibility with other ingredients of the spray composition. Another peservant which can be used is xe2x80x9cSUTTOCIDE Axe2x80x9d which is an hydroxymethylamine derivative.
The stock formulations of the invention are dispersible, and preferably soluble, in water, to produce a spray composition containing by weight a relatively small proportion of the formulation in a relatively large amount of water. The water may contain small amounts of co-solvents or droplet-size modifiers and these are typically surfactants such as lauryl sulphate (which may be added, in proportions of preferably a maximum of about 5 wt %, to alter droplet surface activities or to modify the dissolving capability in respect of specific odour compounds). Although notionally xe2x80x9cdispersiblexe2x80x9d includes possibilities other than being soluble, the latter is very much preferred (and indeed the preferred materials are water-soluble to the extent required).
The formulations are dispersible/soluble in water to produce an aqueous spray compositionxe2x80x94that is to say, a composition which is to be used in a manner in which it is sprayed around, either into the air of the area/volume to be treated or onto a surface to be treated (or adjacent the area/volume to be treated). If the spray composition is to be used to treat a space, it is advantageously in the form of an aerosol (in other words, atomized or finely divided spray), so that the spray droplets float in the atmosphere in the space. The composition is to contain by weight a relatively small proportion of the formulation in a relatively large amount of water. In this context xe2x80x9crelatively smallxe2x80x9d means less than 10 wt %, possibly less than 5 wt %, and preferably about 1 wt %. Indeed, a preferred spray composition contains 1 wt %, of the stock formulation and 99 wt % water. This large proportion of water may seem odd, considering that it is the formulation""s ingredients which are supposed to be dealing with the smells, but in fact it is not so odd. As noted hereinbefore, many smells are hydrophilic substances, and they will readily be adsorbed to the small droplets floating in air (due to the large total surface area of the droplets) and then be dissolved therein. Once they are dissolved, they can be more efficiently neutralised by the formulation""s ingredients that are also dissolved in the droplets.
The surface area of droplets in a given volume of air will be the first and limiting step in the odour-removing process. The odour molecules must diffuse through air and find a droplet before the adsorption and subsequent dissolving steps can take place. The fineness of the spray droplets will thus be important for odour molecules to find a droplet. The concentration of the odour-removing constituents dissolved in water is therefore not thought to be critical as long as the concentration is at 1% or above.
The invention""s stock formulations contain amphoteric material and optionally a drying agent and perhaps a preservant. They can also include relatively small amounts of one or more other materials to enhance ionic strength, add density, add solvating power and change (normally reduce) liquid surface tension. Typical such other materials are pH-neutral inorganic salts, such as potassium chloride and magnesium sulphate, or surfactants such as alcohol or detergents. The preferred quantities for these, when in dry form, are less than 10 wt %, and most preferably around 5 wt %. It is believed that the use of a surfactant, whether an amphoteric surfactant, such as Miranol Ultra, an anionic surfactant, such as lauryl sulphate, or a non-ionic surfactant, such as Brij 35 or Tween 40, or a cationic surfactant, will solubilize hydrophobic odour components and may also alter the surface tension of the liquid. Reducing the liquid surface tension may increase the fineness of the spray droplets.
Formulations may consist of about 60% amphoteric agent (sodium bicarbonate), about 35% drying agent (sodium sulphate+magnesium sulphate) and about 5% to about 10% filler (magnesium sulphate+potassium chloride); or about 60% amphoteric agent (sodium bicarbonate), about 10% drying agent and filler (magnesium sulphate) and about 30% organic completing agent (cyclodextrin)xe2x80x94this formulation being particularly suited to removing odours from textiles; or about 90% amphoteric agent (sodium bicarbonate), about 2% to about 4% drying agent (sodium sulphate+magnesium sulphate), about 2% to about 4% (magnesium sulphate+potassium chloride), and about 4% surfactant (Lauryl sulphate+Miranol Ultra+Brij 35+Tween 40)xe2x80x94this formulation being particularly suitable in removing odours from compost.
It is an important advantage of this invention, compared with many competitive products on the market, that the spray can be used without any masking agent, such as a perfume. Many individuals react negatively to such masking compounds by showing an allergic response.
The stock formulations of the invention can be made by simply mixing the ingredients in a screw mill, and this needs no further discussion at this point.
The invention provides a stock formulation useful in the preparation of a spray deodourizing composition, and it also provides such a spray composition (which can made simply by dispersing or indeed dissolving a relatively small proportion of the formulation in a relatively large amount of water). The invention""s spray compositions can be used to remove smells both from the air within any area/volume and also from almost any kind of surface. Thus, for example, they can be sprayed into a room to remove smells from the air therein, or they can be sprayed directly onto a garment, a carpet or other soft-furnishingsxe2x80x94curtains, sofas and the likexe2x80x94and any powdery residue (from the dissolved substances) later brushed/vacuumed off. No stains are left on the treated materials. Remaining substances left on glass or shiny surfaces treated are easily removed by normal washing/cleaning operations.
In a second aspect, the invention provides a method of interacting with gas at a location, in which an aqueous amphoteric composition is sprayed, preferably as an aerosol, at the location.
Most preferably the amphoteric composition includes sodium bicarbonate as the amphoteric material, and most conveniently is one of those compositions according to the present invention.
The toxicity level of the present preferred spray composition has been kept so low that no harm or irritation should come to users whether by inhalation or contact with the skin, even with extensive daily use. The alkaline nature of the stock formulation and spray composition however (pH 8.5 in water) makes the use of droplet inhalation protection and skin protection advisable for extensive use. The ingredients are used to a large extent in food products or as additives to farming soil. The composition neutralizes a number of materials that, in addition to generating odours, may cause allergic reactions. Moreover, the composition should not react chemically or otherwise damage constructional material, textiles, plastics, or the like.
The preferred spray composition is particularly useful in odour neutralisation work after fires, in forensic cases and the like. Trials have shown that an immediate reduction of odour level can be obtained by a simple water aerosol spray producing a fog in the ambient atmosphere. However, a residual odour always prevailed, as the human nose can detect odours down to very low levels, and the odour level normally increased once the odour-neutralising effect of the moisture particles ceased. On the other hand, with the preferred spray composition of the present invention, a chemical reaction with the odour molecules normally took place irreversibly. Although in very minute amounts, the spray composition spray also left some active material on surfaces (such as fabric, wood, concrete and the like) after spraying, so that not only the airborne odour molecules, but possibly also those adsorbed to those surfaces, were neutralised.
The spray composition is usable for odour neutralisation on the human body, particularly for wound odour neutralisation in hospital. For those purposes, the composition is advantageously isotonic, i.e. has the same osmotic potential as body fluids, whereby it can appropriately be applied on and around wounds.
According to a third aspect of the present invention, there is provided a powder composition comprising as a major ingredient uncoated amphoteric material together with relatively minor amounts of one or more of an alkaline- and/or sulphide-remover, an adsorbant, and a drying agent.
The composition is intended for interacting with gas, which is why it is essential that it is uncoated (as hereinbefore defined), and in particular that it is substantially free of oily matter.
According to a fourth aspect of the present invention, there is provided a powder composition constituting a consumer end product and comprising as a major ingredient amphoteric material together with relatively minor amounts of one or more of an alkaline- and/or sulphide-remover, an adsorbant, and a drying agent.
We have found that if sodium bicarbonatexe2x80x94or, indeed, certain other amphoteric compoundsxe2x80x94is used not as a minor ingredient but as a major one, and if it is used in combination with relatively minor amounts of one or more of an alkali- and/or sulphide-remover (such as iron sulphate), an adsorbant (such as an amorphous mineral, e.g. silica, or a zeolite), and preferably a drying agent (such as sodium sulphate), there can be produced an extremely effective, deodourizing, dry, powder composition that can be spread onto a surface where there is a smell (either on the surface or in the air adjacent that surface), allowed to stand for a time to absorb or neutralise that smell, and then wiped off, taking the smell with it.
The powder compositions of the invention contain as a major (as hereinbefore defined, though in relation to the powder formulation) ingredient amphoteric material (in the form of one or more amphoteric compounds) together with relatively minor amounts of one or more other substances. Particularly-preferred compositions contain about 85% amphoteric material. By xe2x80x9crelatively minorxe2x80x9d is meant, on the same percentage basis, at least some of the material, but not more than 15%, and preferably not more than 10%. Particularly-preferred compositions contain about 3% to about 5% ammonia- and sulphide-remover, about 5% total adsorbant, and about 7% drying agent.
Examples of such particularly preferred compositions are by weight, about 85% sodium bicarbonate, about 3% to about 5% ferrous sulphate, about 7% sodium sulphate and about 5% zeolite; about 85% sodium bicarbonate, about 3% to about 5% zinc sulphate, about 7% sodium sulphate and about 5% zeolite; and about 50% sodium bicarbonate, about 35% zinc oxide, about 3% to about 5% ferrous sulphate, about 7% sodium sulphate and about 5% zeolite.
The invention""s powder compositions contain amphoteric material as their major ingredient. Again, it is particularly advantageous for the amphoteric material to be inorganic, such as a salt, for example sodium bicarbonate or potassium bicarbonate. The amphoteric compound of choice is sodium bicarbonate. Another possible such compound is zinc oxide.
As minor ingredients, the powder compositions of the invention contain one or more of an alkaline-odour and/or sulphide-odour remover, an adsorbant, andxe2x80x94and preferablyxe2x80x94a drying agent. The alkaline-odour and/or sulphide-odour remover is most conveniently iron sulphate (heptahydrate) (typically that material available from SvedaKjemi AS in Norway as xe2x80x9cFERROMELxe2x80x9d). Another possible material can be zinc sulphate. The adsorbant is advantageously insoluble in water and may be one or both of an amorphous silica or a zeolite (typically the amorphous silica available from SvedaKjemi AS in Norway and the zeolite available from Keramika in Slovakia as xe2x80x9cCLINOPTILOLITExe2x80x9d), and the drying agent is conveniently sodium sulphate available from SvedaKjemi AS in Norway, but another possible compound can be potassium sulphate.
Again, no masking agent, such as a perfume, need be added.
Bulk densities and particle sizes of the ingredients of the powder composition are chosen to allow proper mixing, to avoid component segregation, to avoid extensive dust problems when used, and to give good storage properties. Typically, bulk density should be in the 1-3 g/cm3 range, and the particle size in the 0.1-1.0 mm range.
The powder compositions of the invention can be made by simply mixing the ingredients, and this needs no further discussion at this point, save perhaps to note that to achieve a powder either the constituents should themselves already all be in a powder state or the mixture should be made in some appropriate mixing and pulverising apparatus, such as a screw mill.
According to a fifth aspect of the present invention, there is provided in combination, a container of porous, and/or permeable material, and a powder composition according to the invention and in said container.
According to a sixth aspect of the present invention there is provided a method of neutralising odours, in which a powder composition according to the invention is applied to the source of the odour.
According to a seventh aspect of the present invention, there is provided a method of neutralising odours, in which there is applied to the source of the odour a powder composition comprising as a major ingredient amphoteric material together with relatively minor amounts of one or more of an alkaline- and/or sulphide-remover, an adsorbant, and a drying agent.
It is particularly advantageous if a synergistic effect is obtained in respect of neutralisation of an odour.
The powder compositions of the invention can be used to remove odours from an ambient atmosphere; in particular these compositions can be present in air-permeable containers, for example bags, so that the atmosphere can permeate into contact with the compositions.
The powder compositions of the invention can be used to remove smells from almost any kind of surface. Thus, for example, they can be shaken over a carpet or other soft-furnishings (curtains, sofas and the like), and later brushed/vacuumed off and collected up. Similarly, they can be spread over a work surfacexe2x80x94a kitchen table, for instancexe2x80x94and then wiped off after they have done their work. It is very desirable to apply the powder compositions in containers, for example in the form of bags or pads made of porous materials. There may be surfaces where the odour (of substances such as petroleum spirit and diesel oil) is absorbed deep into the porous material (wood or brick, for instance) from which the surface is made. In such cases it may be desirable, if it is possible, to heat the surface (perhaps to 30-45xc2x0 C.) and so assist in the evaporation/outgassing of the odour molecules and their subsequent trapping and neutralisation/removal by the powder composition. In some cases, where the source of the smell is permanentxe2x80x94as with a dry toilet, or a pet""s litter trayxe2x80x94the powder composition is shaken on and simply left there.
The powder composition of the invention can be associated with a foam-forming carrier substance.
Although for applications to sources such as sludge, pets"" litter trays and waste treatment plants the powder compositions of the invention are satisfactory, nevertheless their effect can be improved if they are reformulated into more smell-restraining forms, and particularly foams.
Where a rotting or composting process takes place, volatile gases, such as methane, are formed. The present powder composition interacts with at least some of these volatile gases to bind them. Such gases themselves have little odour, but they carry odour molecules, e.g. sulphides and mercaptans, formed in the process, out into the surrounding air. A dry powder layer on the surface can contribute much to this neutralisation of the odour molecules as they pass through even a very thin dry powder layer on the surface. However, this surface effect can be enhanced if the powder composition is dispersed in a foam layer on the surface. Desirably biodegradable, such a foam containing the powder composition can greatly facilitate the odour neutralisation as it may act as a barrier to the odour molecules (acting as a lid without significantly reducing the access of oxygen); it may also protect the powder composition therein from rainfall and moisture. A good distribution is more easily achieved in this manner.
Accordingly, in an eighth aspect, the present invention provides a method of suppressing odours, wherein an odour-suppressing material in the form of a foam is applied to the source of the odour and wherein the material comprises a foam-form carrier in which is dispersed an odour-suppressing composition according to the invention and active to neutralise the odour.
The powder composition can also be used to remove odours from open air sludge treatment and composting activities as well as for odour removal in closed aerobic and anaerobic reactors.
The toxicity level of the present preferred powder composition has been kept so low that no harm or irritation should come to users whether by inhalation or contact with the skin, even with extensive daily use. However, the alkaline nature of the powder composition (it has a pH of 8.5 in water) makes the employment of dust protection necessary for extensive use. The ingredients are used to a large extent in food products or as additives to farming soil. The composition neutralizes a number of materials that, in addition to generating odours, may cause allergic reactions. Moreover, the composition should not react chemically or otherwise damage constructional material, textiles, plastics, or the like.
The present powder composition is usable in hospitals, homes for elderly people, cars, toilets, boats, tents and caravans, for example.
The treatment of household waste, particularly sewage, and wet organic matter, represents ever-increasing problems in most industrialized countries. Usually, such treatment plants are located in the vicinity of populated regions. Such facilities can be open windrow composting plants or closed reactor systems operated under aerobic or anaerobic conditions. Quite frequently, severe odour problems arise when temperatures and other climatic conditions are unfavourable, or when windrows are turned or opened after long periods generating anaerobic conditions as part of the composting process, or when moved.
In large scale outdoor composting and sludge treatment plants, several odour profiles occur. Amines (fish smell), mercaptans (rotting cabbage), and hydrogen sulphide (rotten eggs) are possibly the most predominant and troublesome components. Considerable methane gas generation also takes place in the plants. Although these gases in themselves may not have strong smells, they often contribute greatly to the spreading of other, much more objectionable odour molecules in the surrounding air. Generally, such plants are of large physical dimensions, and so finding practical solutions to odour problems that can be adapted to the various local conditions and needs is a difficult task. For treatment of off-gassing from closed reactor systems, biofilters and/or wet scrubbers are normally used. The investment and maintenance costs of such systems can be considerable.
Naturally, it is perfectly possible to deal with odours from these sources simply by applying one of the powder compositions of the invention. However, we have found that a particularly advantageous treatment method involves not only such a use of the powder composition but also the spraying into the ambient air around the odour source of an odour-suppressing spray composition, which could be in the form of a powder (even the powder composition of the present invention) or liquid.
In a ninth aspect of the present invention, there is provided a method of suppressing odours from odour-generating solids, comprising applying an odour-suppressing powder composition to said solids and spraying into atmospheric air over said solids an odour-suppressing spray composition.
By this technique, both relatively short-term and relatively long-term suppression of odours emanating from the same solids source can be obtained.
The powder composition and the liquid spray composition of the present invention are particularly suitable for such odour suppression.
Those compositions, moreover, provide the possibility of a flexible approach to such odour problems. When quick action is desirable, the spray composition is better suited. Air-borne odours are usually neutralized within seconds. In outdoor composting plants, and especially during windrow turning operations the air quality improvement can be noticed almost immediately, provided that the spray composition is reasonably well distributed over the areas of the plant where the odour problems are most intense. This can be attained with heavy-duty high-power spray guns.
Odours are generated continuously in such plants, and after spray treatment of the airborne smells, the subsequent generation of smells can be reduced by application of the powder composition, which has an effect over a much longer time interval. The powder composition can also be mixed into the windrows during the turning/aeration process,thus suppressing odours for longer periods while composting or during transport to the end-user. The duration of this effect depends largely on the moisture uptake of the powder composition. The capacity of the powder composition is reduced when the moisture content is high. In many cases, the spray composition can be applied solely, i.e. without use of a powder composition. The spray treatment can be repeated, if desired.